UREI 27-Band graphic equaliser. These are heavy, inductor-based equalisers with a narrow, 1/3rd-octave bandwidth.

1/3rd-octave equalisers were typically used for room EQ back in the 70s and 80s, to equalise the room to a target “room curve”. As that practice fell out of favour, lots of 27-band EQs ended up in studio storerooms, unused

On music signals, individual bands sound like notch filters – which is exactly what they are – but they can be teased into more gentle curves, or abused to radically change the signal